1. Technical Field of the Invention
The present invention relates to a camera which uses a film cartridge encasing a roll of filmstrip, and particularly to a camera having a cartridge holder for accommodating the film cartridge, which is movable between a first position projecting from the camera body for receiving the film cartridge and a second position in which the received film cartridge is accommodated in a predetermined position within the camera body.
2. Description of Related Art
Such cameras are suitable for a film cartridge used new type photographing system having a film ingress/egress slit for feeding out an encased filmstrip and a light-shielding door for opening and closing the slit. While the operation of loading the film cartridge is desired to be easy and quick, it is also desirable that the film cartridge is stably retained in an appropriate position so that the drive is assuringly transmitted to a film spool, but without inhibiting the smooth movement of the cartridge holder between its cartridge accommodating position and projecting position. It is also desired to keep the construction of the camera simple and compact, although the mechanisms for opening/closing the light-shielding door and for winding/rewinding the film generally require a large, complicated structure.
Japanese published unexamined patent application 4-80734 discloses a camera with a cartridge holder having an opening in the upper part for receiving a film cartridge inserted endwise along a shaft of a film roll. The cartridge holder has a fork at its bottom for engaging and driving the shaft of the film roll encased in the film cartridge. The standardized length of the engagement between the fork and the shaft is relatively long, but this does not obstruct the film cartridge loading operation, as the film cartridge is inserted into and removed from the cartridge holder through the opening in the same direction as that of said engagement. However, in order to facilitate the movement of the cartridge holder between its accommodating and projecting positions, the film cartridge is retained in the accommodated position by merely a spring pushing the film cartridge downward within the camera body. Since the shaft of the film roll is not fully supported, stable operation of the film cartridge cannot be ensured. Also, on the one hand the connection and disconnection between the fork member and a fork driving member can be easily accomplished concurrently with the linear movement of the cartridge holder, but on the other hand the cartridge holder needs a relatively large stroke because of its linear movement, causing a troublesome operation.
Japanese published unexamined patent application 4-80735 discloses a camera having a fork disposed within a camera body to reduce the moving volume of a cartridge holder. The fork is retracted from a position where it engages a film spool prior to movement of the cartridge holder between its accommodating and projecting positions, thereby enabling said movement of the cartridge holder. However, the space for retracting the fork needs to have the length more than the aforementioned standard engaging length, causing increase in the size of the camera and the complexity of the structure
Japanese published unexamined patent application 2-114248 discloses a schematic driving system for driving several operations by a single motor. This configuration allows for a simple structure, since several sequential operations of driven members are all driven by the single motor alone. However, the photographing operations described in the above mentioned patent application include only feeding out a filmstrip to a winding spool and taking up the filmstrip by the winding spool, and many other necessary operations such as shutter release and opening/closing of the light-shielding door are not mentioned. Also, the driving force from the motor to each driven member is not individually transmitted. Various photographing operations are related to each other and driven at different speeds, and no mechanism has yet been proposed for satisfactory controlling all these operations by a single motor.
The driving system disclosed in the 2-114248 patent application employs a planetary mechanism. FIG. 31 shows a simplest configuration of such planetary mechanisms. A sun gear S has a coaxial planet carrier C, and a planet gear supported by the planet carrier C is meshed with the sun gear S. When the sun gear S is driven, a friction member provided either between the sun gear S and the planet carrier C or between the planet carrier C and the planet gear P acts on the planet carrier C to pivot with the rotation of the sun gear S, and the planet gear P supported by the planet carrier C revolves around the sun gear S. When the planet gear P comes to contact with any of driven gears D, D provided along the orbit of the planet gear P, the planet gear P engages the driven gear D at a predetermined position and disengages the same by moving away from the predetermined position. By stopping the planet carrier C by a stopper (not shown) when the planet gear P comes to engagement with the driven gear D, the rotation of the sun gear S is transmitted to the planet gear P which drives the driven gear D engaging with the planet gear P. Japanese published unexamined patent application 1-287648 discloses such a planetary mechanism.
However, the mechanism sometimes malfunctions in the following situation. When there are more than three driven gears D, D, one of the driven gears D, D must be placed in line with the sun gear S and the planet gear P as shown in FIG. 31A, in order that the planet gear P can optionally mesh with any of the driven gears D, D along its revolution. When the planet gear P and the driven gear D are coming into contact with each other as shown in FIG. 31B and 31C before they fall into line, one or two addenda of each wheel tend to easily catch each other, coming into a halt. Once the both gears become stationary, they are not able to further rotate in either direction, the addenda blocking each other, unless the sun gear S is rotated in the reverse direction. If the driving force is so strong that the gears S and D are not stopped by their addenda, supporting shafts or teeth of the gears might be damaged. Even when there are only two or fewer gears and no driven gears are placed in line with the gears and S P, as shown in FIG. 31A, the above described blocked condition cannot be fully prevented. Letter A depicts a line between the centers of the sun gear S and the planet gear P, and letter B depicts a line between the centers of the planet gear P and the driven gear D. The nearer the angle made by the lines A, B comes to 180 degree, the more easily the addenda of the gears catch each other.